Containers made of synthetic resin such as polyester have been widely put into practical use for containing beverages. Preforms from which synthetic resin containers are obtained by blow forming have, in recent years, been integrally formed by compression forming by using a compression-forming machine.
In executing the compression forming, the synthetic resin in a molten state as extruded from an extrusion opening of an extrusion nozzle is fed (conveyed) into the compression-forming machine in a manner as described below.
The molten resin is heated and melted in an extruder, and is extruded from the extrusion opening of the extrusion nozzle of the extruder. The molten resin that is extruded is cut by cutting means, and is separated away from the extrusion opening. The molten resin (molten resin to be cut) that is cut is fed onto molten resin conveyer means arranged in a transfer mechanism.
The conveyer means is selectively set to a closed state where it holds the molten resin and to an opened state where it discharges the molten resin that is held to the down side, and further moves about the rotary shaft thereof. The molten resin received by the holding means which is in the closed state moves to a position over a female mold of the compression-forming machine. Thereafter, when the holding means is placed in the opened state, the molten resin is discharged (falls) downward so as to be transferred into the female mold.
The molten resin transferred into the female mold is compression-formed by the cooperation with a male mold of the compression-forming machine, and is formed into a polyester preform of any desired shape for forming a beverage bottle or is formed into various products.
Japanese Patent No. 3674337 proposes an apparatus for cutting the extruded molten resin into a predetermined amount and for feeding it to a metal mold for compression forming. Here, when a polyester resin is treated, a trace amount of volatile components volatilizes from the surface of the extruded molten resin. After operated for extended periods of time, the volatile components adhere on the surfaces of a cutting tool, conveyer means and metal molds; i.e., the components adhered on the surfaces build up thereon permitting resin components of low molecular weights to further deposit thereon. If the resin components deposit, the molten resin easily sticks onto the conveyer means, and the timing for feeding the molten resin to the metal mold varies. With the conventional apparatus for feeding the molten resin, therefore, the molten resin could not be fed to the metal mold maintaining stability for extended periods of time, and the tools and the metal molds had to be cleaned at regular intervals for carrying out the continuous production.
The present invention was accomplished in view of the above circumstances and has an object of providing a method of feeding a molten resin, which can be operated for extended periods of time maintaining stability without permitting the volatile components to deposit on the surfaces of the conveyer means, and an apparatus for feeding the molten resin.